Senses, light, and sight (grade 4) · lesson

How we see

💡 You see an object when light bounces off it and goes into your eyes.

Most things do not make their own light. An apple does not glow.

Light from the sun or a lamp hits the apple. Some of the light bounces off. That bounced light goes into your eyes. Then your brain makes sense of it.

Eyes do not send out light. They only take it in. With no light at all, nothing bounces into your eyes, so you can't see.

🧠 Let's work it out

Trace the light from where it starts.
Lamp, then the book, then your eyes, then your brain.
If any step is missing, you can't see.

What do you think comes next?

reflect: bounce off

Mirrors

💡 A smooth mirror bounces light in a new direction, so light can reach your eyes from things behind you.

A mirror is very smooth and shiny. It reflects almost all the light that hits it.

You see yourself because light bounces off you, hits the mirror, and comes back to your eyes.

You can also see things behind you. Light goes from the thing, to the mirror, to your eyes.

🧠 Let's work it out

Draw the path with your finger.
Start at the thing you see.
Go to the mirror.
Then go to the eyes.
Light never starts at the eyes.

What do you think comes next?

mirror: a smooth, shiny surface that reflects light

From senses to brain to action

💡 Sense organs pick up information, nerves carry it to the brain, and the brain tells the body what to do.

Your body has sense organs. Eyes see light. Ears hear sound. Your nose smells. Your skin feels touch and heat. Your tongue tastes.

Nerves carry messages from your senses to your brain. The brain figures out what the message means.

Then the brain sends a message back along nerves to your muscles. The muscles move.

Touch a hot pan. Skin nerves sense heat. A message races along your nerves. Your muscles pull your hand away.

🧠 How to think about it

Put the steps in order: sense, nerves, brain, action. The action always comes last.

nerve: a thin path that carries messages through your body
brain: the organ that takes in messages and decides what the body does

How animals use their senses

💡 Animals use their senses to get information about the world and act on it to survive.

Animals use their senses to find food and stay safe.

An owl hears a mouse under leaves. Its brain works out where the mouse is. Then the owl swoops down.

A bat makes high sounds and listens for echoes. The echoes tell its brain where things are in the dark.

A cat's whiskers are touch sensors. When they brush a chair, the cat knows something is close.

🧠 Let's work it out

Ask three things.
What sense is used?
What does the brain learn from it?
What does the animal do next?

What do you think comes next?

echo: a sound that bounces back